//! Implementation of a simple key-value store using IndexedDB for WebAssembly
//! and an in-memory store for testing.

use crate::core::kvs::error::{KvsError, Result};
use serde::{de::DeserializeOwned, Serialize};
use std::collections::HashMap;
use std::sync::{Arc, Mutex};

#[cfg(target_arch = "wasm32")]
use {
    idb::{Database, DatabaseEvent, Factory, TransactionMode},
    js_sys::Promise,
    wasm_bindgen::prelude::*,
    wasm_bindgen_futures::JsFuture,
};

#[cfg(target_arch = "wasm32")]
impl From<JsValue> for KvsError {
    fn from(err: JsValue) -> Self {
        KvsError::Other(format!("JavaScript error: {:?}", err))
    }
}

/// A simple key-value store.
///
/// In WebAssembly environments, this uses IndexedDB.
/// In non-WebAssembly environments, this uses an in-memory store for testing.
#[derive(Clone)]
pub struct KvsStore {
    #[cfg(not(target_arch = "wasm32"))]
    data: Arc<Mutex<HashMap<String, String>>>,
    
    #[cfg(target_arch = "wasm32")]
    db: Arc<Database>,
    
    #[cfg(target_arch = "wasm32")]
    store_name: String,
}

impl KvsStore {
    /// Opens a new key-value store with the given name.
    ///
    /// # Arguments
    ///
    /// * `db_name` - The name of the database
    /// * `store_name` - The name of the object store
    ///
    /// # Returns
    ///
    /// A new `KvsStore` instance
    #[cfg(not(target_arch = "wasm32"))]
    pub async fn open(_db_name: &str, _store_name: &str) -> Result<Self> {
        // In non-WASM environments, use an in-memory store for testing
        Ok(Self {
            data: Arc::new(Mutex::new(HashMap::new())),
        })
    }

    #[cfg(target_arch = "wasm32")]
    pub async fn open(db_name: &str, store_name: &str) -> Result<Self> {
        let factory = Factory::new()?;
        let mut db_req = factory.open(db_name, Some(1))?;

        db_req.on_upgrade_needed(|event| {
            let db = event.database()?;
            if !db.object_store_names().includes(&JsValue::from_str(store_name)) {
                db.create_object_store(store_name, None)?;
            }
            Ok(())
        })?;

        let db = Arc::new(db_req.await?);
        
        Ok(Self {
            db,
            store_name: store_name.to_string(),
        })
    }

    /// Stores a value with the given key.
    ///
    /// # Arguments
    ///
    /// * `key` - The key to store the value under
    /// * `value` - The value to store
    ///
    /// # Returns
    ///
    /// `Ok(())` if the operation was successful
    #[cfg(not(target_arch = "wasm32"))]
    pub async fn set<K, V>(&self, key: K, value: &V) -> Result<()>
    where
        K: ToString,
        V: Serialize,
    {
        let key_str = key.to_string();
        let serialized = serde_json::to_string(value)?;
        
        let mut data = self.data.lock().unwrap();
        data.insert(key_str, serialized);
        
        Ok(())
    }

    #[cfg(target_arch = "wasm32")]
    pub async fn set<K, V>(&self, key: K, value: &V) -> Result<()>
    where
        K: ToString + Into<JsValue>,
        V: Serialize,
    {
        let tx = self.db.transaction(&[&self.store_name], TransactionMode::ReadWrite)?;
        let store = tx.object_store(&self.store_name)?;
        
        let serialized = serde_json::to_string(value)?;
        store.put_with_key(&JsValue::from_str(&serialized), &key.into())?;
        
        JsFuture::from(tx.done()).await?;
        Ok(())
    }

    /// Retrieves a value for the given key.
    ///
    /// # Arguments
    ///
    /// * `key` - The key to retrieve the value for
    ///
    /// # Returns
    ///
    /// The value if found, or `Err(KvsError::KeyNotFound)` if not found
    #[cfg(not(target_arch = "wasm32"))]
    pub async fn get<K, V>(&self, key: K) -> Result<V>
    where
        K: ToString,
        V: DeserializeOwned,
    {
        let key_str = key.to_string();
        let data = self.data.lock().unwrap();
        
        match data.get(&key_str) {
            Some(serialized) => {
                let value = serde_json::from_str(serialized)?;
                Ok(value)
            },
            None => Err(KvsError::KeyNotFound(key_str)),
        }
    }

    #[cfg(target_arch = "wasm32")]
    pub async fn get<K, V>(&self, key: K) -> Result<V>
    where
        K: ToString + Into<JsValue>,
        V: DeserializeOwned,
    {
        let tx = self.db.transaction(&[&self.store_name], TransactionMode::ReadOnly)?;
        let store = tx.object_store(&self.store_name)?;
        
        let request = store.get(&key.into())?;
        let promise = Promise::from(request);
        let result = JsFuture::from(promise).await?;
        
        if result.is_undefined() {
            return Err(KvsError::KeyNotFound(key.to_string()));
        }
        
        let value_str = result.as_string().ok_or_else(|| {
            KvsError::Deserialization("Failed to convert value to string".to_string())
        })?;
        
        let value = serde_json::from_str(&value_str)?;
        Ok(value)
    }

    /// Deletes a value for the given key.
    ///
    /// # Arguments
    ///
    /// * `key` - The key to delete
    ///
    /// # Returns
    ///
    /// `Ok(())` if the operation was successful
    #[cfg(not(target_arch = "wasm32"))]
    pub async fn delete<K>(&self, key: K) -> Result<()>
    where
        K: ToString,
    {
        let key_str = key.to_string();
        let mut data = self.data.lock().unwrap();
        
        if data.remove(&key_str).is_some() {
            Ok(())
        } else {
            Err(KvsError::KeyNotFound(key_str))
        }
    }

    #[cfg(target_arch = "wasm32")]
    pub async fn delete<K>(&self, key: K) -> Result<()>
    where
        K: ToString + Into<JsValue>,
    {
        let tx = self.db.transaction(&[&self.store_name], TransactionMode::ReadWrite)?;
        let store = tx.object_store(&self.store_name)?;
        
        // First check if the key exists
        let request = store.count_with_key(&key.into())?;
        let promise = Promise::from(request);
        let result = JsFuture::from(promise).await?;
        
        let count = result.as_f64().unwrap_or(0.0);
        if count <= 0.0 {
            return Err(KvsError::KeyNotFound(key.to_string()));
        }
        
        store.delete(&key.into())?;
        
        JsFuture::from(tx.done()).await?;
        Ok(())
    }

    /// Checks if a key exists in the store.
    ///
    /// # Arguments
    ///
    /// * `key` - The key to check
    ///
    /// # Returns
    ///
    /// `true` if the key exists, `false` otherwise
    #[cfg(not(target_arch = "wasm32"))]
    pub async fn contains<K>(&self, key: K) -> Result<bool>
    where
        K: ToString,
    {
        let key_str = key.to_string();
        let data = self.data.lock().unwrap();
        
        Ok(data.contains_key(&key_str))
    }

    #[cfg(target_arch = "wasm32")]
    pub async fn contains<K>(&self, key: K) -> Result<bool>
    where
        K: ToString + Into<JsValue>,
    {
        let tx = self.db.transaction(&[&self.store_name], TransactionMode::ReadOnly)?;
        let store = tx.object_store(&self.store_name)?;
        
        let request = store.count_with_key(&key.into())?;
        let promise = Promise::from(request);
        let result = JsFuture::from(promise).await?;
        
        let count = result.as_f64().unwrap_or(0.0);
        Ok(count > 0.0)
    }

    /// Lists all keys in the store.
    ///
    /// # Returns
    ///
    /// A vector of keys as strings
    #[cfg(not(target_arch = "wasm32"))]
    pub async fn keys(&self) -> Result<Vec<String>> {
        let data = self.data.lock().unwrap();
        
        Ok(data.keys().cloned().collect())
    }

    #[cfg(target_arch = "wasm32")]
    pub async fn keys(&self) -> Result<Vec<String>> {
        let tx = self.db.transaction(&[&self.store_name], TransactionMode::ReadOnly)?;
        let store = tx.object_store(&self.store_name)?;
        
        let request = store.get_all_keys(None)?;
        let promise = Promise::from(request);
        let result = JsFuture::from(promise).await?;
        
        let keys_array = js_sys::Array::from(&result);
        let mut keys = Vec::new();
        
        for i in 0..keys_array.length() {
            let key = keys_array.get(i);
            if let Some(key_str) = key.as_string() {
                keys.push(key_str);
            } else {
                // Try to convert non-string keys to string
                keys.push(format!("{:?}", key));
            }
        }
        
        Ok(keys)
    }

    /// Clears all key-value pairs from the store.
    ///
    /// # Returns
    ///
    /// `Ok(())` if the operation was successful
    #[cfg(not(target_arch = "wasm32"))]
    pub async fn clear(&self) -> Result<()> {
        let mut data = self.data.lock().unwrap();
        data.clear();
        
        Ok(())
    }

    #[cfg(target_arch = "wasm32")]
    pub async fn clear(&self) -> Result<()> {
        let tx = self.db.transaction(&[&self.store_name], TransactionMode::ReadWrite)?;
        let store = tx.object_store(&self.store_name)?;
        
        store.clear()?;
        
        JsFuture::from(tx.done()).await?;
        Ok(())
    }
}